Field of the Invention
The present invention relates to a method for making contact with a doping region of a semiconductor component.
Semiconductor components are formed in a silicon substrate, for example. To that end, capacitors, resistors or transistors are formed, inter alia, in the semiconductor substrate. Furthermore, conductive regions are produced in the semiconductor substrate by the introduction of a dopant into the semiconductor substrate. The doped regions have an increased conductivity and are used as electrical terminals for the components formed in the semiconductor substrate. In subsequent processing steps, different doping regions are electrically connected to one another by interconnects.
The electrical wiring is usually formed in such a way that first an insulating layer is deposited on a surface of the semiconductor substrate and contact holes are subsequently formed in the insulating layer. The contact holes usually extend from the surface of the insulating layer as far as a surface of a doped region to be connected, the surface of the doped region to be connected being uncovered by the contact hole. A metal-containing layer, for example, is subsequently deposited on the insulating layer and in the contact hole on the doping region. Afterwards, a thermal step in a nitrogen-containing atmosphere is usually carried out, in the course of which two process aims are achieved simultaneously. First, a part of the metal-containing layer reacts with the silicon of the doping region to form a silicide layer and, second, the non-siliconized part of the metal-containing layer reacts to form a metal-nitride-containing layer.
The method steps specified above are disclosed for example in the reference titled “Nitridation of Polycrystalline Titanium As Studied By In Situ Angle-Resolved X-ray Photoelectron Spectroscopy”, by A. Ermolieff et al., Surface and Interface Analysis, Vol. 11, p. 563-568 (1988); in the reference titled “Influence Of The Sputtering Method Of TiN/Ti Films On The Resistance Of High Aspect Ratio Contact Holes”, by R. Kanamura et al., VMIC Conference Abstracts, p. 554-559 (1996); in the reference titled “Tungsten Contacts For 256M DRAM Process Using A Thermally Formed TiN Diffusion Barrier”, by J. Gambino et al., VMIC Conference Abstracts, p. 180i-180k (1996); in the reference titled “Ion Metal Plasma (IMP) Deposited Titanium Liners For 0.25 and 0.18 μm Multilevel Interconnects”, Proceedings of IEEE International Electron Devices Meeting, (1996) and in the reference titled “Integrated IMP Ti And MOCVD TiN For 300 mm W Barrier And Liners For Sub 0.18 μm IC Processing”, Proceedings of SPIE, Volume 3883, p. 130-136, (1999).
What is disadvantageous about the known methods, however, is that the resistance at the bottom of the contact hole is formed with a relatively high value. This is due to the continually decreasing feature sizes in the semiconductor industry and the associated increase in the aspect ratio of the contact hole, which quantifies the ratio of contact hole depth to contact hole diameter.
One disadvantage of the prior art is that the silicide layer formed has an excessively thin thickness and, consequently, the electrical resistance when making contact with the doping region is relatively high. This leads to unacceptable delay times for example in the propagation time of electrical signals, as a result of which the electrical circuit and the component become unusable.